1. Field of the Invention
The present invention relates to an ultrasonic diagnosis apparatus which uses, for example, a biplane ultrasonic transducer to transmit and receive ultrasonic waves to and from a subject under examination and obtains ultrasonic cross-sectional images in two orthogonal scanning planes of the subject.
2. Description of the Related Art
The use of ultrasonic waves permits acquisition of cross-sectional images and blood flow information of a subject under examination. An ultrasonic imaging apparatus is constructed from an ultrasonic probe having an ultrasonic transducer, an ultrasonic-wave transmitting-receiving circuit system, a signal processing circuit, and a display unit. Upon receipt of an excitation pulse from the ultrasonic-wave transmitting-receiving circuit system, the ultrasonic transducer of the ultrasonic probe transmits ultrasonic waves. The reflected waves are received by the same transducer, so that a received signal is obtained. The received signal is processed by the signal processing circuit and then visually displayed by the display unit.
As such an apparatus there is what is referred to as an electronic scanning type apparatus. This type of apparatus uses an ultrasonic transducer comprised of a large number of electro-acoustic transducing elements, such as piezoelectric elements, which are arranged side by side. By driving each of the elements with a different amount of delay, ultrasonic waves are focused and deflected whereby an ultrasonic cross-sectional image can be obtained in real time.
Ultrasonic probes include probes for body cavity imaging and probes for body surface imaging, which are variously used, depending on the imaging desired. The body-cavity ultrasonic probe has an ultrasonic transducer to which a multiconductor cable is connected. The ultrasonic transducer is incorporated into one end of a bar. An operator holds the other end of the bar by hand and inserts the ultrasonic-wave transmitting-receiving plane of the ultrasonic transducer into such a body cavity as the anus of a subject under examination. The body-surface ultrasonic probe also has an ultrasonic transducer. The ultrasonic transducer is connected with a multiconductor cable and housed in a probe case. An operator holds the probe case by hand and puts the ultrasonic-wave transmitting-receiving plane of the ultrasonic transducer to the surface of a body region, such as the abdomen, of the subject.
The imaging of a body region is attained by obtaining a cross-sectional image in one scanning plane by the use of the body-cavity ultrasonic probe or the body-surface ultrasonic probe. An apparatus which is adapted to obtain cross-sectional images in two orthogonal planes and thus well suited for diagnosis has come into use recently.
Hereinafter a body-cavity ultrasonic probe and a body-surface ultrasonic probe which are adapted for imaging of two orthogonal planes will be described with reference to the drawings. Such a probe is also referred to as a biplane probe. That is, the body-cavity ultrasonic probe 1, as shown in FIG. 1, is designed so that an operator can hold the other end of a bar 22 by hand and insert the ultrasonic-wave transmitting-receiving plane of an ultrasonic transducer 1--1 into a body cavity. The ultrasonic transducer unit 1--1 comprises an ultrasonic transducer group 1A for obtaining a cross-sectional image in a lateral scanning plane A and an ultrasonic transducer group 1B for obtaining a cross-sectional image in a longitudinal plane B. In this case, the ultrasonic transducers groups 1A and 1B are made orthogonal to each other in the direction in which their elements are arranged, so that the scanning plane A and the scanning plane B are orthogonal to each other. In the present example, the ultrasonic transducer group 1A and the ultrasonic transducer group 1B are spaced as shown. The distance between the transducer group 1A and the transducer group 1B is d. In the case of sector scanning, the distance d stands for the distance between the ape of the sector scanning plane A and the apex of the sector scanning plane B, but not the distance 1 between the end of the transducer group 1A and the end of the transducer group 1B. In the present example, the distance d between the apex of the sector scanning plane A and the apex of the sector scanning plane B stands for the distance between the center of the elements of the transducer group 1A and the center of the elements of the transducer group 1B.
The body-surface ultrasonic probe 10, on the other hand, has an ultrasonic transducer unit 10-1 with substantially the same structure as the transducer unit shown in FIG. 1. The ultrasonic transducer unit 10-1 comprises ultrasonic transducer groups 10A and 10B. In the present example, the transducer group 10A and the transducer group 10B are disposed very close to each other. The distance between the transducer 10A and the transducer 10B is d'. In the case of sector scanning, the distance d, as in FIG. 1, stands for the distance between the apex of the sector scanning plane A and the apex of the sector scanning plane B, but not the distance 1 between the end of the transducer group 1A and the end of the transducer group 1B. In the present example, the distance 1 is substantially zero.
In the above examples, with the body-cavity ultrasonic probe 1, the transducer groups 1A and 1B are disposed with a space therebetween, while, with the body-surface ultrasonic probe 10, the transducer groups 10A and 10B are disposed very close to each other. Alternatively, the transducer groups 10A and 10B may be disposed very close to each other in the body-surface ultrasonic probe 10, while the transducer groups 1A and 1B may be disposed with a space therebetween in the body-cavity ultrasonic probe 1.
As shown in FIG. 2, the ultrasonic transducer unit 10-1 is incorporated in an end of a probe case 10-2. A cable 10-3 emerges from the other end of the probe case 10-2. FIG. 3A and FIG. 3B are a front view and a side view of the body-surface ultrasonic probe 10 and FIG. 3b, respectively. As can be seen from FIGS. 3A and 3B, cross-sectional images in the orthogonal scanning planes A and B can be obtained by putting the ultrasonic transducer 10-1 of the body-surface ultrasonic probe 10 to the body surface.
As described above, the transducer groups 1A and 1B in the body-surface ultrasonic probe 1 are disposed with a distance d therebetween, while the transducer groups 10A and 10B in the body-surface ultrasonic probe 10 are disposed with a distance d' therebetween. For this reason, in order to obtain a cross-sectional image in the scanning plane B after a cross-sectional image in the scanning plane A has been obtained, the probe must be moved to a position in the scanning plane B. This will impose a burden on an operator and the examination will be prolonged.
With either of the body-cavity ultrasonic probe 1 and the body-surface ultrasonic probe 10, switching between the ultrasonic transducers is required in order to display a cross-sectional image in a scanning plane after the display of a cross-sectional image in the other scanning plane. The probe must then be moved to a desired position for display of the cross-sectional image in the former scanning plane. It is therefore difficult for an operator to understand the scanning plane of a cross-sectional image which is being displayed on the display screen. Thus, it becomes difficult to make diagnosis efficiently and moreover the examination takes a long time.